text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Watchdog driver for the K3 RTI module
   *
   * (c) Copyright 2019-2020 Texas Instruments Inc.
   * All rights reserved.
   */
  
  #include <linux/clk.h>
  #include <linux/device.h>
  #include <linux/err.h>
  #include <linux/io.h>
  #include <linux/kernel.h>
  #include <linux/mod_devicetable.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/platform_device.h>
  #include <linux/pm_runtime.h>
  #include <linux/types.h>
  #include <linux/watchdog.h>
  
  #define DEFAULT_HEARTBEAT 60
  
  /* Max heartbeat is calculated at 32kHz source clock */
  #define MAX_HEARTBEAT	1000
  
  /* Timer register set definition */
  #define RTIDWDCTRL	0x90
  #define RTIDWDPRLD	0x94
  #define RTIWDSTATUS	0x98
  #define RTIWDKEY	0x9c
  #define RTIDWDCNTR	0xa0
  #define RTIWWDRXCTRL	0xa4
  #define RTIWWDSIZECTRL	0xa8
  
  #define RTIWWDRX_NMI	0xa
  
  #define RTIWWDSIZE_50P		0x50
  #define RTIWWDSIZE_25P		0x500
  #define RTIWWDSIZE_12P5		0x5000
  #define RTIWWDSIZE_6P25		0x50000
  #define RTIWWDSIZE_3P125	0x500000
  
  #define WDENABLE_KEY	0xa98559da
  
  #define WDKEY_SEQ0		0xe51a
  #define WDKEY_SEQ1		0xa35c
  
  #define WDT_PRELOAD_SHIFT	13
  
  #define WDT_PRELOAD_MAX		0xfff
  
  #define DWDST			BIT(1)
  
  static int heartbeat = DEFAULT_HEARTBEAT;
  
  /*
   * struct to hold data for each WDT device
   * @base - base io address of WD device
   * @freq - source clock frequency of WDT
   * @wdd  - hold watchdog device as is in WDT core
   */
  struct rti_wdt_device {
  	void __iomem		*base;
  	unsigned long		freq;
  	struct watchdog_device	wdd;
  };
  
  static int rti_wdt_start(struct watchdog_device *wdd)
  {
  	u32 timer_margin;
  	struct rti_wdt_device *wdt = watchdog_get_drvdata(wdd);
  
  	/* set timeout period */
  	timer_margin = (u64)wdd->timeout * wdt->freq;
  	timer_margin >>= WDT_PRELOAD_SHIFT;
  	if (timer_margin > WDT_PRELOAD_MAX)
  		timer_margin = WDT_PRELOAD_MAX;
  	writel_relaxed(timer_margin, wdt->base + RTIDWDPRLD);
  
  	/*
  	 * RTI only supports a windowed mode, where the watchdog can only
  	 * be petted during the open window; not too early or not too late.
  	 * The HW configuration options only allow for the open window size
  	 * to be 50% or less than that; we obviouly want to configure the open
  	 * window as large as possible so we select the 50% option.
  	 */
  	wdd->min_hw_heartbeat_ms = 500 * wdd->timeout;
  
  	/* Generate NMI when wdt expires */
  	writel_relaxed(RTIWWDRX_NMI, wdt->base + RTIWWDRXCTRL);
  
  	/* Open window size 50%; this is the largest window size available */
  	writel_relaxed(RTIWWDSIZE_50P, wdt->base + RTIWWDSIZECTRL);
  
  	readl_relaxed(wdt->base + RTIWWDSIZECTRL);
  
  	/* enable watchdog */
  	writel_relaxed(WDENABLE_KEY, wdt->base + RTIDWDCTRL);
  	return 0;
  }
  
  static int rti_wdt_ping(struct watchdog_device *wdd)
  {
  	struct rti_wdt_device *wdt = watchdog_get_drvdata(wdd);
  
  	/* put watchdog in service state */
  	writel_relaxed(WDKEY_SEQ0, wdt->base + RTIWDKEY);
  	/* put watchdog in active state */
  	writel_relaxed(WDKEY_SEQ1, wdt->base + RTIWDKEY);
  
  	return 0;
  }
  
  static int rti_wdt_setup_hw_hb(struct watchdog_device *wdd, u32 wsize)
  {
  	/*
  	 * RTI only supports a windowed mode, where the watchdog can only
  	 * be petted during the open window; not too early or not too late.
  	 * The HW configuration options only allow for the open window size
  	 * to be 50% or less than that.
  	 */
  	switch (wsize) {
  	case RTIWWDSIZE_50P:
  		/* 50% open window => 50% min heartbeat */
  		wdd->min_hw_heartbeat_ms = 500 * heartbeat;
  		break;
  
  	case RTIWWDSIZE_25P:
  		/* 25% open window => 75% min heartbeat */
  		wdd->min_hw_heartbeat_ms = 750 * heartbeat;
  		break;
  
  	case RTIWWDSIZE_12P5:
  		/* 12.5% open window => 87.5% min heartbeat */
  		wdd->min_hw_heartbeat_ms = 875 * heartbeat;
  		break;
  
  	case RTIWWDSIZE_6P25:
  		/* 6.5% open window => 93.5% min heartbeat */
  		wdd->min_hw_heartbeat_ms = 935 * heartbeat;
  		break;
  
  	case RTIWWDSIZE_3P125:
  		/* 3.125% open window => 96.9% min heartbeat */
  		wdd->min_hw_heartbeat_ms = 969 * heartbeat;
  		break;
  
  	default:
  		return -EINVAL;
  	}
  
  	return 0;
  }
  
  static unsigned int rti_wdt_get_timeleft_ms(struct watchdog_device *wdd)
  {
  	u64 timer_counter;
  	u32 val;
  	struct rti_wdt_device *wdt = watchdog_get_drvdata(wdd);
  
  	/* if timeout has occurred then return 0 */
  	val = readl_relaxed(wdt->base + RTIWDSTATUS);
  	if (val & DWDST)
  		return 0;
  
  	timer_counter = readl_relaxed(wdt->base + RTIDWDCNTR);
  
  	timer_counter *= 1000;
  
  	do_div(timer_counter, wdt->freq);
  
  	return timer_counter;
  }
  
  static unsigned int rti_wdt_get_timeleft(struct watchdog_device *wdd)
  {
  	return rti_wdt_get_timeleft_ms(wdd) / 1000;
  }
  
  static const struct watchdog_info rti_wdt_info = {
  	.options = WDIOF_KEEPALIVEPING,
  	.identity = "K3 RTI Watchdog",
  };
  
  static const struct watchdog_ops rti_wdt_ops = {
  	.owner		= THIS_MODULE,
  	.start		= rti_wdt_start,
  	.ping		= rti_wdt_ping,
  	.get_timeleft	= rti_wdt_get_timeleft,
  };
  
  static int rti_wdt_probe(struct platform_device *pdev)
  {
  	int ret = 0;
  	struct device *dev = &pdev->dev;
  	struct resource *wdt_mem;
  	struct watchdog_device *wdd;
  	struct rti_wdt_device *wdt;
  	struct clk *clk;
  	u32 last_ping = 0;
  
  	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
  	if (!wdt)
  		return -ENOMEM;
  
  	clk = clk_get(dev, NULL);
  	if (IS_ERR(clk))
  		return dev_err_probe(dev, PTR_ERR(clk), "failed to get clock\n");
  
  	wdt->freq = clk_get_rate(clk);
  
  	clk_put(clk);
  
  	if (!wdt->freq) {
  		dev_err(dev, "Failed to get fck rate.\n");
  		return -EINVAL;
  	}
  
  	/*
  	 * If watchdog is running at 32k clock, it is not accurate.
  	 * Adjust frequency down in this case so that we don't pet
  	 * the watchdog too often.
  	 */
  	if (wdt->freq < 32768)
  		wdt->freq = wdt->freq * 9 / 10;
  
  	pm_runtime_enable(dev);
  	ret = pm_runtime_get_sync(dev);
  	if (ret) {
  		pm_runtime_put_noidle(dev);
  		return dev_err_probe(dev, ret, "runtime pm failed\n");
  	}
  
  	platform_set_drvdata(pdev, wdt);
  
  	wdd = &wdt->wdd;
  	wdd->info = &rti_wdt_info;
  	wdd->ops = &rti_wdt_ops;
  	wdd->min_timeout = 1;
  	wdd->max_hw_heartbeat_ms = (WDT_PRELOAD_MAX << WDT_PRELOAD_SHIFT) /
  		wdt->freq * 1000;
  	wdd->parent = dev;
  
  	watchdog_set_drvdata(wdd, wdt);
  	watchdog_set_nowayout(wdd, 1);
  	watchdog_set_restart_priority(wdd, 128);
  
  	wdt_mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	wdt->base = devm_ioremap_resource(dev, wdt_mem);
  	if (IS_ERR(wdt->base)) {
  		ret = PTR_ERR(wdt->base);
  		goto err_iomap;
  	}
  
  	if (readl(wdt->base + RTIDWDCTRL) == WDENABLE_KEY) {
  		u32 time_left_ms;
  		u64 heartbeat_ms;
  		u32 wsize;
  
  		set_bit(WDOG_HW_RUNNING, &wdd->status);
  		time_left_ms = rti_wdt_get_timeleft_ms(wdd);
  		heartbeat_ms = readl(wdt->base + RTIDWDPRLD);
  		heartbeat_ms <<= WDT_PRELOAD_SHIFT;
  		heartbeat_ms *= 1000;
  		do_div(heartbeat_ms, wdt->freq);
  		if (heartbeat_ms != heartbeat * 1000)
  			dev_warn(dev, "watchdog already running, ignoring heartbeat config!\n");
  
  		heartbeat = heartbeat_ms;
  		heartbeat /= 1000;
  
  		wsize = readl(wdt->base + RTIWWDSIZECTRL);
  		ret = rti_wdt_setup_hw_hb(wdd, wsize);
  		if (ret) {
  			dev_err(dev, "bad window size.\n");
  			goto err_iomap;
  		}
  
  		last_ping = heartbeat_ms - time_left_ms;
  		if (time_left_ms > heartbeat_ms) {
  			dev_warn(dev, "time_left > heartbeat? Assuming last ping just before now.\n");
  			last_ping = 0;
  		}
  	}
  
  	watchdog_init_timeout(wdd, heartbeat, dev);
  
  	ret = watchdog_register_device(wdd);
  	if (ret) {
  		dev_err(dev, "cannot register watchdog device\n");
  		goto err_iomap;
  	}
  
  	if (last_ping)
  		watchdog_set_last_hw_keepalive(wdd, last_ping);
  
  	return 0;
  
  err_iomap:
  	pm_runtime_put_sync(&pdev->dev);
  	pm_runtime_disable(&pdev->dev);
  
  	return ret;
  }
  
  static int rti_wdt_remove(struct platform_device *pdev)
  {
  	struct rti_wdt_device *wdt = platform_get_drvdata(pdev);
  
  	watchdog_unregister_device(&wdt->wdd);
  	pm_runtime_put(&pdev->dev);
  	pm_runtime_disable(&pdev->dev);
  
  	return 0;
  }
  
  static const struct of_device_id rti_wdt_of_match[] = {
  	{ .compatible = "ti,j7-rti-wdt", },
  	{},
  };
  MODULE_DEVICE_TABLE(of, rti_wdt_of_match);
  
  static struct platform_driver rti_wdt_driver = {
  	.driver = {
  		.name = "rti-wdt",
  		.of_match_table = rti_wdt_of_match,
  	},
  	.probe = rti_wdt_probe,
  	.remove = rti_wdt_remove,
  };
  
  module_platform_driver(rti_wdt_driver);
  
  MODULE_AUTHOR("Tero Kristo <t-kristo@ti.com>");
  MODULE_DESCRIPTION("K3 RTI Watchdog Driver");
  
  module_param(heartbeat, int, 0);
  MODULE_PARM_DESC(heartbeat,
  		 "Watchdog heartbeat period in seconds from 1 to "
  		 __MODULE_STRING(MAX_HEARTBEAT) ", default "
  		 __MODULE_STRING(DEFAULT_HEARTBEAT));
  
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:rti-wdt");
  